In 1987, the concept of PhC was proposed separately by E. Yablonovitch from United States Bell Labs who discussed how to suppress spontaneous radiation and by S. John from Princeton University who made discussions about photonic localization. The PhC is a material structure in which dielectric materials are arranged periodically in space, and is usually an artificial crystal consisting of two or more materials having different dielectric constants.
With the emergence of and in-depth research on photonic crystal, people can control the motion of photons in a PhC material more flexibly and effectively. In combination with traditional semiconductor processes and integrated circuit technologies, design and manufacture of PhC and devices thereof have continually and rapidly marched towards all-optical processing, and the PhC has become a breakthrough for photonic integration. In December 1999, the PhC was recognized by the American influential magazine Science as one of the top-ten scientific advances in 1999, and therefore has become a hot topic in today's scientific research field.
An all-optical logic device mainly includes an optical amplifier-based logic device, a non-linear loop-mirror logic device, a Sagnac-interference-type logic device, a ring-cavity logic device, a multi-mode-interference logic device, an optical waveguide-coupled logic device, a photoisomerized logic device, a polarization-switch optical-logic device, a transmission-grating optical-logic device, etc. These optical-logic devices have the common shortcoming of large size in developing large-scale integrated optical circuits. With the improvement of science and technology in recent years, people have also done research and developed quantum optical-logic devices, nanomaterial optical-logic devices and PhC optical-logic devices, which all conform to the dimensional requirement of large-scale photonic integrated optical circuits. For modern manufacturing processes, however, the quantum optical-logic devices and the nanomaterial optical-logic devices are very difficult to be manufactured, whereas the PhC optical-logic devices have competitive advantages in terms of manufacturing process.
In recent years, PhC logic devices have become a hot area of research drawing widespread attentions, and it is highly likely for them to replace the current widely-applied electronic logic devices in the near future. The PhC logic device can directly realize all-optical logical functions, such as “AND”, “OR”, “NOT” and the like, and is a core device for realizing all-optical computing. In the process of realizing all-optical computing, PhC logical function devices based on “AND”, “OR”, “NOT”, “XOR” and the like have been successfully designed and studied, and various complex logic components are still needed for achieving the goal of all-optical computing.